Snd 24.5:
in s7, added (settable) symbol-initial-value (the #_... value)
changed invalid-escape-function to invalid-exit-function
new *s7* fields: symbol-quote?, symbol-printer, and make-function
added function-arglist
in sublet, varlet and s7_load_with_environment, () is no longer
an abbreviation for (rootlet)
checked: sbcl 2.4.5, gsl 2.8